Fujitsu R410A Service Instruction page 32

Trouble shooting 7
INDOOR UNIT Error Method:
Indoor Heat Ex. Thermistor Error
Detective Actuators:
Indoor Unit Controller PCB
Heat Exchanger (MID) Thermistor
Forecast of Cause:
1. Connector failure connection
Test 1 : Check connection of Connector
Check if connector is loose or removed
Check erroneous connection
Check if thermistor cable is open
Reset Power when reinstalling due to removed connector or incorrect wiring.
>>
OK
Test 2 : Remove connector and check Thermistor resistance value
Thermistor Characteristics (Rough value)
Temperature (°C )
Temperature (°F )
Resistance value (k )
Temperature (°C )
Temperature (°F )
Resistance value (k )
If Thermistor is either open or shorted, replace it and reset the power.
OK
Test 3 : Check voltage of Controller PCB (DC5.0V)
Make sure circuit diagram of each indoor unit and check terminal voltage at Thermistor (DC5.0V)
RED
1 1
1 1
CN3
2 2
2 2 WHITE
3 3
BLACK
1 1
CN1
BLACK
2 2
If the voltage does not appear, replace Controller PCB and execute the check operation again.
Indicate or Display:
Outdoor Unit : No indication
Indoor Unit
ERROR CODE : [E : 42]
Detective details:
Indoor unit thermistor is open or short is detected always.
2. Thermistor failure
0 5 10 15
32 41 50 59
176.0 134.2 103.3 80.3
40 45 50
104 113 122
25.6 20.9 17.1
BLACK
THERMISTOR
( PIPE TEMP. )
BLACK
THERMISTOR
( ROOM TEMP. )
02-09
: Operation lamp: 4 times Flash, Timer lamp: 2 times Flash
Economy lamp: Continuous flash.
3. Controller PCB failure
20 25 30
68 77 86
62.9 49.7 39.6
35
95
31.7